1. Field of the Invention
This invention relates to a novel radiation sensitive screen.
2. Description of the Prior Art
As a typical example of sensitive screens to be used in the storage mode, there has heretofore been the target of a photoconductive pickup tube shown in FIG. 1. This tube is made up of a light transmitting substrate 1 usually termed the faceplate, a transparent conductive film 2, a photoconductor layer 3, an electron gun 4 and an envelope 5. The optical image of incident light 7 formed on the photoconductor layer 3 through the faceplate 1 is subjected to photoelectric conversion and stored in the surface of the photoconductor layer 3 as a charge pattern. The stored charges are read in time series by the use of a scanning electron beam 6.
An important property required of the photoconductor layer 3 at this time is that the charge pattern does not vanish due to diffusion within the time interval in which a specified picture element is scanned by the scanning electron beam 6 (in other words, the storage time). As the materials of the photoconductor layer 3, accordingly, there are ordinarily employed semiconductors whose specific resistances are at least 10.sup.10 .OMEGA..cm, for example, Sb.sub.2 S.sub.3 -, PbO- or Se-based chalcogen glass. In case of employing a material such as Si single crystal whose specific resistance is lower than 10.sup.10 .OMEGA..cm, the surface of the photoconductor layer on the electron beam scanning side needs to be divided into the mosaic so as to prevent the vanishing of the charge pattern. Among these materials, the Si single crystal involves a complicated working process. The high resistivity semiconductors are inferior in the photo-response characteristics because they usually contain at high densities trap levels impeding the transit of photo-carriers. The imaging device is accordingly apt to the drawback that a long decay lag or an after-image develops.
The following references are cited to show the state of the prior art:
(1) Weimer et al., Electronics, 23, 5 (1950) PA1 (2) Weimer et al., RCA Rev., 12, 314 (1951) PA1 (3) Singer, B., IEEE Trans., ED-18, 11, 1016 (1971) PA1 (4) Miyashiro, S. et al., IEEE Trans., ED-18, 11, 1023 (1971) PA1 (5) S.M. Blumenfeld et al., IEEE Trans., ED-18, 11, 1036 (1971)
The above references concern vidicons. PA2 This relates to a silicon vidicon tube. PA2 This relates to a silicon electron multiplication camera tube. PA2 This relates to an epitaxial diode array vidicon.